As mobile systems are gaining more and more importance in every aspect of the life, be it business or everyday use, the need for highly available services appeared in this area too. In fixed infrastructures, the computer clusters have been extensively used to provide such services. For example, a special type of computer clusters, the high availability clusters, inherently is designed to support fault tolerance for applications. This ability makes them look suitable for the mobile environment too; however, the increased dynamicity and limited resources impose new challenges that did not exist before. In this paper, we analyze how a service availability middleware and applications, based on the Application Interface Specification (AIS) of the Service Availability Forum (SA Forum,) can be adapted to tolerate relatively frequent configuration/environmental changes, and to support provision of services in these environments. These results were achieved in the HIDENETS IST-FP6-STREP project funded by the European Union, where SA Forum specifications are used to provide the necessary services in the infrastructure domain, hence the consortium tried to take advantage of them in the ad-hoc (mobile) domain as well.